Single-Ply Roofing: The Ultimate Guide

The story of single-ply roofing systems dates back to the 1970’s oil crisis and the search for a roofing system less reliant on asphalt material led to lightweight, flexible roof membranes. Today, these systems have evolved into a variety of single ply systems, including TPO, PVC and EPDM.

Single-ply membranes are usually broken down into two subgroups — thermoplastics and thermosets. Thermoplastics have a common characteristic not found in synthetic rubbers — they can be heated and reshaped or melted multiple times. Because of this, the most common method of seaming a thermoplastic is by heat-welding the membrane. Properly melting the edges together fuses the membrane into a strongly bonded seam. The two major thermoplastic membranes in the market are polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO).

Thermoplastics
TPO membranes have become widely used as roof membranes in the past ten years. A TPO roofing membrane is typically made from polypropylene and ethylene-propylene (EP) rubber polymerized together using state-of-the-art polymer manufacturing technology. Unlike some other popular thermoplastic roofing membranes, the TPO polymer does not contain chlorine and no chlorine-containing ingredients are added during sheet production. Because TPO membranes are inherently flexible, unlike PVC membranes, additional plasticizers are not required in the formulation so there is little danger of plasticizer migration.

Thermosets
Virtually all thermoset roof membranes are EPDM. Once EPDM has cured, it cannot be melted and reshaped. Consequently, the rubber membrane is seamed by an adhesive — generally either a field-applied contact cement or an adhesive tape that is applied in the field or factory and activated by removing a release paper. A major benefit of EPDM is that it can stretch and relax, so it can easily accommodate thermal expansion and contraction on large expanses of roof.

Reflectivity
The majority of thermoplastics come in white. These white membranes give an initial high reflectance value that can help keep the temperature of the roof and consequently the inside of the building cooler. As the roof becomes older and collects dirt, however, this initial value will decrease unless the roof is periodically cleaned (see a case study at our website http://bit.ly/hby3NJ). Thermosets are available with a white surface, but most likely comes as a dark grey, almost black color.

For more information regarding single-ply roofing systems, give RAMCON a call at (877) 726-2661 or visit our Single Ply Roofing section at the RAMCON website.